Serrapinnus is a genus of small characins (family Characidae) native to river systems across Brazil, Argentina, Paraguay, Bolivia, Uruguay, and French Guiana - broadly the Amazon, Paraná-Paraguay, and Atlantic coastal drainages of South America. Atlas species run from 0.5–3.5 in, deep-bodied, laterally compressed, and silvery, often described informally as 'mini tetras.' They typically shoal in slow currents, floodplain pools, and vegetated stream margins.
Several species have a place in the aquarium hobby as peaceful, undemanding schooling tetras: Sterba's tetra (S. sterbai) and the blackline tetra (S. notomelas) are established in the trade for their sparkling coloration and calm temperament in a community tank, while the piaba (S. piaba) takes its name from a term used broadly in Brazil for small, silvery characins collected commercially. The conservation picture is comparatively favorable for the genus - the atlas tally is led by 9 Least Concern species against 7 Not Evaluated, with no species carrying CARES status, suggesting a diverse but relatively low-profile group rather than one under active threat.